VMware has released a paper titled: Configuration Examples and Troubleshooting for VMDirectPath. The paper which contains 5 pages details some configuration examples on how to configure direct access to an I/O device within ESX using VMDirectPath. VMDirectPath allows you to connect up to two passthrough devices to a virtual machine improving performance for ESX systems that utilize high-speed I/O devices.
VMDirectPath is supported running on Intel Xeon 5500 systems, featuring Virtual Technology for Directed I/O (VT-d) which is an implementation of the I/O memory management unit (IOMMU) or experimental support on AMD platforms using I/O Virtualization Technology (AMD IOMMU).
The paper documents the steps needed to enable VMDirectPath, by enabling the functionality in the BIOS, verifying that IOMMU is enabled within ESX and editing the VMX file for advanced configuration. The paper also details some potential problems, like device assignment dependencies, virtual IRQ sharing and physical IRQ sharing.